In the method for producing propylene oxide by epoxidating propylene, as a method for recovering propylene and propylene oxide in the vent gas discharged from the separation step after the epoxidation reaction, it has been suggested to contact the gas discharged from the separation step with an alcohol such as methanol, a glycol, a cyclic ether, a glycol ether or a ketone to recover propylene and propylene oxide and to recycle propylene (see, for example, Patent document 1: WO 01/57009).